The present invention pertains to a device as well as to a process for mixing at least a first gas component with a second gas component. Such a device can be used especially as a gas mixer in a portable respirator.
A device of the type mentioned has been known from DE 199 07 362 A1, in which ambient air is drawn in as a second gas component via a channel by means of a venturi nozzle, through which a propellant gas is led as a first gas component, wherein a partial flow of the first gas component is likewise drawn in via the channel via an additional bypass line. If pure oxygen is used as the propellant gas, an average oxygen concentration arising from the partial flows of the pure oxygen as the first gas component and the ambient air as the second gas component becomes established at the gas outlet of the venturi nozzle. Due to the fact that the pure oxygen as a propellant gas is the first gas component, it is utilized optimally, and the volume of the pressurized gas cylinder for the oxygen can be kept as small as possible.
The fact that the oxygen concentration in the gas mixture can be changed to a limited extent only proved to be a drawback of the prior-art device. For example, the gas mixture has a higher oxygen concentration than necessary during the respiration of infants or during respiration with high volume flows. In the first case the ejector cannot produce a sufficient suction flow for fluid dynamic reasons and in the second case the necessary high volume flow can be generated only by the increased inflow of oxygen from the pressurized gas cylinder.
The object of the present invention is to provide a device and a process for mixing at least two gas components such that the particularly necessary concentration of the first gas component can be brought about at different volume flows of the gas mixture generated as a result.
The device and the process are suitable for mixing at least a first gas component with a second gas component. The device has a plurality of ejectors of different sizes, which are designed according to the principle of a venturi nozzle. A propellant gas flow of up to 5 liters per minute (L/minute) and a suction flow of up to 30 liters per minute (L/minute) can be generated with a smaller ejector, and a propellant gas flow of up to 10 liters per minute (L/minute) and a suction flow of up to 60 liters per minute (L/minute) can be generated with a larger ejector. Liters per minute (L/minute) always means hereinafter normal liters per minute (NL/minute) in order to indicate a variable that is independent from the pressure and the temperature. The ejectors have propellant gas connections for feeding the first gas component from a propellant gas container and suction channels for feeding the second gas component from a mixing chamber, as well as gas outlets to a respiration connection. The mixing chamber itself is supplied with the second gas component via a central suction channel. Proportional valves, which regulate the feed of the first gas component via the propellant gas connections, are arranged in the propellant gas connections. A volume flow sensor each is arranged in the central suction channel for the second gas component and directly before the respiration connection. The first volume flow sensor in the central suction channel measures the volume flow of the second gas component, and the second volume flow sensor directly before the respiration connection measures the volume flow of the gas mixture consisting of all the gas components.
The volume flow sensors and the proportional valves are connected via lines to an evaluating and control unit, which evaluates the signals of at least the second volume flow sensor and correspondingly actuates the proportional valves. In the case of a signal of up to about 20 liters per minute (L/minute) to be measured by the second volume flow sensor, the first proportional valve before the smaller ejector is actuated for opening by the evaluating and control unit. In the case of a signal to be measured between about 20 liters per minute (L/minute) and about 45 liters per minute (L/minute), the evaluating and control unit actuates the second proportional valve before the larger ejector for opening, and in the case of a signal to be measured above 45 liters per minute (L/minute), both proportional valves are actuated for opening.
To ensure that the second gas component always reaches the ejectors via the suction channels, nonreturn valves, which prevent gas components from an ejector that is not in operation because of the closed proportional valve arranged upstream in the corresponding propellant gas connection from reaching the other ejector via the mixing chamber or the central suction channel for the second gas component, are arranged in all suction channels in a preferred embodiment.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.